The invention in particular relates to a guide vane assembly.
In engines, for example turbomachines and in particular gas turbine engines, it is generally known to provide adjustable guide vanes for influencing the flow depending on the rotational speed of rotating rotor blades. In particular in gas turbine engines, usually adjustable guide vanes are used in the area of the compressor, wherein the guide vanes are adjusted depending on the compressor's rotational speed. In the technical jargon, the adjustable guide vanes are referred to as variable stator vanes, or VSV, in short.
Here, the adjustable guide vanes usually represent a component of a guide vane row and are arranged inside a housing in which the rotating rotor blades are also arranged. In practice, the individual guide vanes are mounted at the housing so as to be respectively adjustable via a bearing journal. Provided inside the housing is usually a rotatable bearing of a guide vane at a hub, e.g. of a compressor. Each bearing journal is mounted in a rotatable manner at the housing inside an associated bearing opening in the wall of the housing. At that, the bearing journal passes through this bearing opening along an extension direction of the bearing journal, so that an end of the bearing journal is accessible at an outer side of the housing for adjusting the corresponding guide vane by turning the bearing journal. At that, usually respectively one lever, which is affixed at an adjusting element in the form of an adjusting ring of an adjusting mechanism, engages at a journal end to simultaneously adjust multiple guide vanes by adjusting the adjusting element and multiple levers that are hinged thereat. Such a generic guide vane assembly with adjustable guide vanes for a compressor of a gas turbine engine is shown in U.S. Pat. No. 9,309,778 B2, for example. In practice, the bearing journals of the guide vanes, which are often also referred to as shingles, are provided in radially protruding sleeve-shaped bearing extensions of the housing. These bearing extensions are formed at a wall of the housing and ensure the rotatable mounting and support of the bearing journal.
The at least one adjusting element of the adjusting appliance provided for adjustment of the guide vanes is usually supported at an outer side of the housing and is adjustable relative to the same in the circumferential direction to cause a rotation of the guide vanes about their respective rotational axis. To keep the adjusting element at a defined radial distance to the outer side of the housing during that process, it is known to provide one or multiple compensation devices. Here, a compensation device is primarily provided for the purpose of avoiding that, during operation of the engine in which the housing is heated up stronger than the adjusting element depending on the respective cycle, the housing displaces the adjusting element radially outwards, and in this manner the adjusting precision of the adjusting element is reduced, or even a deformation or a jamming of the adjusting element occurs. A radial distance of the adjusting element to the outer side of the housing is predefined via a compensation device, and different thermal expansions of the adjusting element, on the one hand, and of the housing, on the other, are compensated to keep the adjusting element in a defined position relative to the housing, e.g. to keep a ring-shaped adjusting element centered with respect to the housing. For this purpose, for example multiple compensation devices are arranged in a manner distributed along the circumferential direction to support the adjusting element at different positions against the housing and to center it with respect to the same.
What is for example known from DE 10 2014 219 552 A1 is a compensation device with a spacer that is supported inside a compensation element in the form of a bushing. This bushing has a higher thermal expansion coefficient than the adjusting element and its spacer via which the adjusting element can be supported at an outer side of the housing. During operation of the engine, the housing of the guide vane assembly as well as the bushing that is functioning as a compensation element as well as the adjusting element are heated up. Here, the thermal expansion of the bushing leads to a radially outward displacement of the spacer attached thereat, while the thermal expansion of the adjusting element and of the spacer lead to a displacement radially inwards. What thus results due to the higher thermal expansion coefficient of the bushing is a temperature-related outward radial displacement of the spacer, which substantially corresponds to the radial elongation of the housing that occurs as a result of the temperature. The different thermal expansions of the housing and of the adjusting element are thus substantially compensated, and a radial distance between the spacer and the outer side of the housing is kept substantially constant. In this manner, a centering of the adjusting element with respect to the housing can also be maintained during operation of the engine.
However, in the guide vane assembly known from DE 10 2014 219 552 A1, the mounting of the compensation device is comparatively elaborate. In particular the spacer has to be positioned almost exactly relative to the bushing and the adjusting element to achieve the desired compensation. In addition, the bushing is inserted into a through bore of the adjusting element, so that when designing the individual components of the compensation device, it must in particular be taken into account with some effort as to what kind of heat transfer results between the adjusting element and the bushing placed herein.